JP2010139389A - Capacitance type position detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a capacitance type position detector which performs integration processing with a signal obtained from a mover and can obtain position data with high resolution. <P>SOLUTION: A reference signal S1 from an exciting circuit 30 and a detection signal S2 outputted from the capacitance type position detector 100 are shaped in a waveform respectively. The signals S1 and S2 shaped in the waveform are inputted respectively to an integration type phase difference measuring circuit 51 and electric angle data are computed. The computed electric angle data are converted into the position data by an electric angle-position converting means 52. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a detector for detecting the relative rotational position of a fixed and non-rotating stator and a rotating rotor, and in particular, a rotational position can be obtained with high resolution by interpolating a signal obtained from the rotor. The present invention relates to a capacitive position detector.

  A capacitive position detector is known as a sensor that detects rotation information of a rotating body. Capacitance type position detectors can acquire rotation information of a rotating body with high sensitivity using high-frequency signals, and can use a thin electrode structure because of the principle of capacitive coupling. The device can be downsized.

  The capacitance type position detector disclosed in Patent Document 1 includes a rotating plate that is rotatably attached to a main body by a rotating shaft, and a rotating plate 12 that is attached to the main body so as to be opposed to the rotating plate. Including the rotational displacement of the rotating plate relative to the rotating plate.

On the surface of the fixed plate, a plurality of transmission electrodes are arranged at equal intervals along the circumferential direction. A plurality of unit electrode groups each having an 8-phase electrode as a unit are formed on the transmission electrode by applying a sine wave or a rectangular wave sequentially shifted in a predetermined phase by a voltage application circuit.
Further, the same number of reception electrodes as the unit electrode groups are arranged on the surface of the rotating plate so as to face each of the predetermined continuous transmission electrodes included in each unit electrode group.

JP 61-105421 A

  In the capacitive position detector, a plurality of transmission electrode plates are arranged at equal intervals, an alternating voltage with a predetermined phase is applied to each excitation electrode, and a coupling electrode is arranged opposite to these excitation electrodes. The relative position between the excitation electrode and the coupling electrode is obtained by analyzing the period of the capacitance signal detected from the coupling electrode. Because of the small size and light weight, there is an increasing need to obtain the position detection of a moving body such as a rotating body with high accuracy using a capacitance type position detector.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a capacitive position detector capable of obtaining position data with high resolution by performing integration processing with a signal obtained from a moving element.

  The invention according to claim 1 of the present application includes a stator and a movable element that moves relative to the stator, and the stator includes a plurality of excitation electrodes that are periodically arranged and electrically independent from each other. A plurality of sets of excitation electrodes, and a receiving electrode electrically independent of the excitation electrodes, and the movable element includes a plurality of coupling electrodes periodically disposed to face the excitation electrodes. A transmission electrode disposed opposite to the reception electrode to which all of the plurality of coupling electrodes are electrically connected; and the movable element has the same number of coupling electrodes as the excitation electrode group. Applying excitation signals having the same frequency and different phases to the respective excitation electrodes of the excitation electrode group, and detecting signals detected by the reception electrodes that change according to the relative positions of the stator and the mover, and The excitation signal applied to the excitation electrode A phase difference measurement circuit that measures a phase difference with a reference signal that is any one of the above, and a capacitance type that detects a relative position of the moving element based on the phase difference measured by the phase difference measurement circuit A position detector, wherein the phase difference measurement circuit starts outputting a predetermined current in a first case where a state of the predetermined reference signal and the detection signal is established, and the predetermined reference signal A current supply circuit that stops current output in the second case where the state of the signal and the detection signal is established, a capacitor that stores current from the current supply circuit, and a voltage across the terminals of the capacitor in the second case Is held and sampled and a completion signal is output after completion of sampling. A discharge circuit that discharges the charged electric charge, a voltage-electric angle conversion circuit that converts the voltage data obtained by the sampling into electrical angle data corresponding to a phase difference, and outputs the electrical angle data as provisional electrical angle data, and electrical angle data A register A and a register B to be stored; and a difference comparison processing unit for evaluating a relationship between the provisional electrical angle data and the previous provisional electrical angle data stored in the register A, and the difference The comparison processing unit uses the absolute value of the velocity of the moving element less than the value obtained by dividing 1/2 period of one excitation electrode group by the time interval with respect to the time interval for numerically acquiring the phase difference. When the electrical angle change amount, which is a difference obtained by subtracting the previous provisional electrical angle data from the provisional electrical angle data, is greater than −180 degrees and less than +180 degrees, the data stored in the register B is The data held in the register A is updated to the provisional electrical angle data. When the electrical angle change amount is −180 degrees or less, the data held in the register B is updated. Add one cycle, update the data held in the register A to the provisional electrical angle data, and subtract one cycle from the data held in the register B when the electrical angle change amount is +180 degrees or more The data held in the register A is updated to the provisional electrical angle data, the data in the register A is output as electrical angle data in one cycle, and the data in the register B is output as cycle number data. A capacitance type position detector comprising: a conversion circuit that converts an output from the phase difference measurement circuit into position data.

  The invention according to claim 2 includes a time gate circuit that outputs a binary time gate signal having the meanings of “valid” and “invalid”, and the time gate signal is within one cycle of a predetermined reference signal. When the time gate signal is valid, the current supply circuit is valid when the feature point appears once and becomes invalid when the feature point appears once within a predetermined period of the detection signal. The hold / sample circuit is controlled to perform a hold operation and a sampling operation when the time gate signal becomes invalid after the time gate signal becomes valid after being controlled to output a predetermined current. The capacitance type position detector according to claim 1.

  The invention according to claim 3 includes a time gate circuit that outputs a binary time gate signal having the meanings of “valid” and “invalid”, and the time gate signal is a period of the predetermined detection signal. This is a signal that becomes valid with a feature point that appears once within, and becomes invalid with a feature point that appears once within one period of a predetermined reference signal, and the current supply circuit is effective when the time gate signal is valid. The hold / sample circuit is controlled to perform a hold operation and a sampling operation when the time gate signal becomes invalid after the time gate signal becomes valid after being controlled to output a predetermined current. The capacitance type position detector according to claim 1.

  According to the present invention, it is possible to provide a capacitive position detector capable of obtaining position data with high resolution by performing integration processing using a signal obtained from a moving element.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram for explaining a stator used in a capacitive position detector. The stator 10 is a disk-shaped fixing plate having a stator through-hole 15 in the center, and a plurality of excitation electrodes 11 extending in the radial direction of the stator 10 are provided at regular intervals on one surface thereof. They are electrically connected to each other at regular intervals. The excitation electrode 11 is excited by a multiphase power source corresponding to the period, and a traveling wave voltage is generated at a predetermined phase on the surface of the stator 10 provided with the excitation electrode 11.

  The stator 10 may be a substrate material having an insulating surface and rigidity. For example, a glass epoxy material, a paper-bakelite laminated material, a ceramic such as glass or alumina, a metal such as iron or aluminum, or a semiconductor such as silicon. Any material may be used as long as the plate is thermally sprayed with ceramic, coated with an insulating resin, or insulated beads are arranged to float to form an air layer.

  Each conductor such as the excitation electrode 11 provided on the stator 10 is formed by removing a conductor such as rolled copper foil or vapor-deposited chrome by photo-etching, or a conductive ink such as silver or carbon is inkjet, silkscreen, or offset printing. Etc. can be formed.

  In the example of FIG. 1, four excitation electrodes 11 constitute one excitation electrode group 16, and ten excitation electrode groups 16 are formed as a whole. The excitation electrodes 11 in the same order included in each excitation electrode group 16 are electrically connected to each other, and the wiring is shown as a solid line or a broken line in the drawing. The wiring shown by the solid line is arranged on the same surface as the surface on which the excitation electrode 11 is provided, and the wiring shown by a broken line is arranged on the surface opposite to the surface on which the excitation electrode 11 is provided. ing.

  In the example of FIG. 1, every fourth excitation electrode 11 is electrically connected to each other via a current carrying conductor 12 and a power feeding conductor 13. And the excitation electrode 11 of each phase is excited by the excitation means which has four phases. Since the four excitation electrodes 11 constituting one excitation electrode group 16 are electrically independent from each other, a through-hole technique is used to electrically connect the excitation electrodes 11 of each excitation electrode group 16. Each excitation electrode 11, each ring-shaped conducting conductor 12, and each feeding conductor 13 are electrically connected. The through-hole technique is a technique generally used as a printed board manufacturing technique.

  A ring-shaped receiving electrode 14 that is electrically independent of the excitation electrode 11 is provided on the surface of the stator 10 on which the excitation electrode 11 is formed. The reception electrode 14 is provided with a detection signal output unit 17 for outputting the received detection signal to the outside.

  In FIG. 1, the receiving electrode 14 is disposed on the same surface as the excitation electrode 11 and on the inner peripheral side. It is not necessary to dispose on the same surface side as the excitation electrode, and it may be provided on the opposite surface. Further, the reason why the receiving electrode 14 is provided on the inner peripheral side is that it is disposed opposite to the transmitting electrode 22 of the moving element 20, and when the transmitting electrode 22 is disposed on the outer peripheral side, the receiving electrode 14 is disposed on the stator. 10 on the outer peripheral side.

  Further, the stator through-hole 15 formed in the stator 10 is not an indispensable constituent element of the capacitive position detector, but is a structure for convenience of use, and the stator through-hole in use. If the hole 15 is not necessary, it may not be provided.

  FIG. 2 is a diagram for explaining a moving element used in the capacitive position detector. The moving element 20 is a disk-shaped rotating body in which a through-hole 23 of the moving element is formed at the center, and a plurality of coupling electrodes 21 extending in the radial direction of the moving element 20 are formed on one surface thereof. In the example shown in FIG. 2, ten coupling electrodes 21 are provided. All of these coupling electrodes 21 are electrically connected to a ring-shaped transmission electrode 22 formed at the center of the moving element 20 to constitute a single-phase detection electrode.

  Then, by positioning the stator 10 and the mover 20 so that the surface of the stator 10 on which the excitation electrode 11 is formed and the surface of the mover 20 on which the coupling electrode 21 is formed, a plurality of couplings are obtained. The detection electrode composed of the electrode 21 detects the traveling wave voltage generated in the excitation electrode 11 on the stator 10 side by the principle of electrostatic induction.

  The signal detected by the detection electrode changes depending on the charge of the plurality of excitation electrodes 11 having different phases of the stator 10 and the degree of coupling of the coupling electrode 21, and as a result of the synthesis, the relative angular position of the stator 10 and the movable element 20. It appears as a single-phase AC signal with a phase determined by. When the mover 20 rotates and moves by the number of phases of the excitation electrode 11, a single-phase AC signal having the same phase as the first is generated, and when it further moves, the phase change is repeated.

  Therefore, focusing attention on the phase difference between the phase of the specific phase of the excitation electrode 11 and the phase of the detected single-phase AC signal, the phase difference is determined when the position of the coupling electrode is set to one period of the excitation electrode group. It can be detected as 0 to 360 degrees, and a position of 360 degrees or more can be grasped by counting how many times the change in the phase difference is repeated.

  The single-phase alternating current signal detected by the detection electrode constituted by the coupling electrode 21 of the mover 20 is electrostatically induced between the transmission electrode 22 provided on the mover 20 and the reception electrode 14 provided on the stator 10. Then, the signal is transmitted from the transmission electrode 22 of the mover 20 to the reception electrode 14 of the stator 10. The transmission electrode 22 and the reception electrode 14 can transmit a detection signal in a non-contact manner. As a method for transmitting the detection signal from the moving element 20 to the stator 10 side, there is a method using a slip ring or a rotating transformer in addition to electrostatic induction.

  FIG. 3 is a schematic configuration diagram of a capacitive position detector including a stator and a mover. The moving element 20 is supported by a mechanism (not shown) so that the surface on which the coupling electrode 21 is disposed faces the excitation electrode 11 of the stator 10 with a predetermined gap and is rotatable concentrically with the moving element 20. . The gap between the opposing surfaces of the stator 10 and the moving element 20 is generally set to about 150 μm to 200 μm when the arrangement pitch of the excitation electrodes 11 is 200 μm, for example.

  The four phases A, B, C, and D, which are alternating voltages from the excitation circuit 30, are fixed via the A-phase power feeding unit 18a, the B-phase power feeding unit 18b, the C-phase power feeding unit 18c, and the D-phase power feeding unit 18d. The AC voltages connected to the current-carrying conductors 12 of the respective phases of the child 10 are supplied to the excitation electrodes 11 of the respective phases of the stator 10 via the feeding conductors 13 by a quarter period.

  Since each excitation electrode 11 faces each coupling electrode 21 and is capacitively coupled, a voltage signal corresponding to the degree of electrostatic coupling between each excitation electrode 11 and each coupling electrode 21 appears on the transmission electrode 22. Further, since the transmission electrode 22 and the reception electrode 14 are opposed to each other, a signal of a voltage corresponding to the degree of the electrostatic induction appears as the detection signal S2 on the reception electrode 14 by electrostatic induction. The detection signal S <b> 2 is a single-phase AC signal having the same frequency as the multiphase AC voltage input from the excitation circuit 30 to the excitation electrode 11. For example, if the frequency of the multiphase AC voltage of the excitation circuit 30 is 1 MHz, the detection signal is also a 1 MHz single-phase AC signal. The detection signal S2 received by the reception electrode 14 is output from the detection signal output unit 17 to the phase detection circuit 40.

  The voltage of one phase of the four-phase AC voltage output from the excitation circuit 30 is used as a reference signal S1, and the phase of this reference signal is transmitted from the transmission electrode 22 of the moving element 20 and received by the receiving electrode 14 of the stator. The phase difference from the phase of the detected signal S2 is detected by the phase detection circuit 40. From the phase difference between the reference signal S1 and the detection signal S2, the relative positions of the stator 10 and the mover 20 can be obtained. FIG. 3 shows that the D phase of the excitation circuit 30 is the reference signal S1, and the phase difference from the detection signal S2 is detected by the phase detection circuit 40. The reference signal S1 may be selected from any one phase of the excitation circuit 30.

  FIG. 4 is a diagram for explaining the phase difference between the reference signal input to the detection circuit and the detection signal. The illustrated phase difference changes depending on the relative positional relationship (mechanical phase) between the stator 10 and the movable element 20. As shown in FIG. 4, the detection signal S2 is delayed by the phase difference compared to the reference signal S1. FIG. 4 shows the relationship between the reference signal and the detection signal at a certain moment. When both signals are observed continuously, the phase difference does not change when the moving element 20 is stopped with respect to the stator 10. However, the phase difference continuously changes when the actuator is moving. The phase difference varies from 0 degrees to 360 degrees depending on the degree of coupling (in other words, the relative positional relationship) between the excitation electrode 11 of the stator 10 and the coupling electrode 21 of the moving element 20. Further, if the direction of movement is reversed, the direction of the phase difference also changes.

  FIG. 5 is a schematic block diagram of the present invention. The reference signal S1 that is an output signal from the excitation circuit 30 and the detection signal S2 by the capacitive position detector 100 are shaped by the waveform shapers 32 and 33, respectively. Each waveform-shaped signal is input to an integral phase difference measurement circuit 51, and the integral phase difference measurement circuit 51 calculates electrical angle data. The calculated electrical angle data is converted into position data by the electrical angle-position converting means 52.

FIG. 6 is a schematic configuration diagram of an integral phase difference measurement circuit 51 that measures the phase difference between the reference signal S1 and the detection signal S2. One phase of the four-phase excitation voltages of the excitation circuit 30 is defined as a reference signal S1 (hereinafter simply referred to as “reference signal S1”) that is converted into a rectangular wave by a waveform shaper 32 such as a limiter amplifier. On the other hand, the detection signal S2 detected by the capacitive position detector 100 is also converted into a rectangular wave detection signal S2 (hereinafter simply referred to as “detection signal S2”) by the waveform shaper 33 such as a limiter amplifier. Signal waveforms of the reference signal S1 and the detection signal S2 are shown in FIG. As described above, the characteristic point is obtained by converting the reference signal S1 and the detection signal S2 into a square wave by a limiter amplifier as described above and taking the rising or falling timing (see FIG. 8). Further, the reference signal S1 before waveform shaping and the detection signal S2 before waveform shaping are binarized at a predetermined threshold level by a comparator (not shown), and the transition from 0 to 1 or from 1 to 0 is performed. The transition may be a feature point (see FIG. 8).
In addition, the reference signal S1 before waveform shaping and the detection signal S2 before waveform shaping are made signals from which a DC offset has been removed through an AC coupling circuit. Alternatively, a zero cross point passing from plus to minus may be used as the feature point.
By these methods, each signal is defined as one point for one period. Furthermore, the feature points of the reference signal S1 and the feature points of the detection signal S2 are not limited to being obtained by the same method, and the above methods may be combined.

  The reference signal S <b> 1 and the detection signal S <b> 2 formed into a rectangular wave are input to the integral type phase difference measurement circuit 51. In the integral type phase difference measuring circuit 51, first, the time gate circuit 510 generates the time gate signal S3. As shown in FIG. 7, the time gate signal S3 is 1 from the rising time of the reference signal S1 to the rising time of the detection signal S2, and is 0 at other times. “1” of the time gate signal S3 means valid and “0” means invalid. Note that a configuration example of the time gate circuit 510 is shown in FIG.

  While the time gate signal S3 is 1, the current supply circuit 511 continues to supply current to the capacitor 512. When the time gate signal S3 changes from “1” to “0”, the hold / sample circuit 513 holds the voltage across the capacitor 512, samples it, and digitizes the voltage. When the digitization is completed, the hold / sample circuit 513 outputs a completion signal to the discharge circuit 514. Specifically, a CRD (Current Regular diode), a current mirror type constant current circuit, or the like can be used as the current supply circuit. Focusing on reproducibility, the linearity can be corrected separately, and it can be constituted by a constant voltage source and a resistor. For these switch elements, semiconductor switch elements are used, and FET elements are particularly suitable. 9 and 10 show examples of current supply circuits.

  When the hold / sample circuit 513 outputs a completion signal, the discharge circuit 514 switches one end of the capacitor 512 connected to the current supply circuit 511 to the ground, and discharges the electric charge accumulated in the capacitor 512 to make it empty. When the discharge is completed, the discharge circuit 514 reconnects one end of the capacitor 512 connected to the ground in the previous operation to the current supply circuit 511.

  The voltage data digitized by the hold / sample circuit 513 is represented as Vc [V]. Separately from Vc [V], Vc360 [V], which is a capacitor terminal voltage determined by the circuit design of the current supply circuit 511 and the time of one excitation cycle, is prepared. Alternatively, Vc360 [V] may be obtained by charging the capacitor with the current of the current supply circuit 511 for a time corresponding to one excitation cycle (electrical angle 360 degrees) and sampling the resulting voltage.

Electrical angle data is calculated from the above Vc [V] and Vc 360 [V]. As an example,
Electrical angle data = 360 * (Vc [V] / Vc360 [V]). The electrical angle data obtained here is referred to as provisional electrical angle data S4 for convenience of explanation.

  Next, the provisional electrical angle data S4 is input to the difference comparison processing unit 517. The difference comparison processing unit 517 uses two registers (register A516 and register B518) to perform processing for obtaining the current position of the object to be measured. The difference comparison processing unit 517 can be configured using a subtraction circuit or the like. Further, the difference comparison processing unit 517 evaluates a difference value obtained by subtracting the value of the register A516 that is the previous provisional electrical angle data from the provisional electrical angle data S4. Note that the difference comparison processing unit 517 can be performed by processing by a processor or a circuit configuration.

The frequency of the excitation signal from the excitation circuit 30 is determined in consideration of the moving speed (rotational speed) of the object to be measured. The time required to change the position of the electrical angle of 360 degrees is determined to be sufficiently longer than one period of the excitation signal. Under this condition, the difference between the electrical angle data obtained this time and the obtained electrical angle data is 180 degrees or more only when the electrical angle spans one cycle due to movement.
Accordingly, the change amount of the position larger than one cycle and the change amount of the position within one cycle are obtained as follows.

1) When the difference is larger than −180 degrees and smaller than +180 degrees, provisional electrical angle data S4 is stored in the register A516 that stores the position within one cycle. In this case, since it can be determined that the movement over one period has not been performed, the value of the register B 518 for storing the number of periods is not changed (the initial values of both registers are zero).
2) When the difference is +180 degrees or more, the temporary electrical angle data S4 is stored in the register A516, and the data stored in the register B518 is subtracted by 1 and stored.
3) When the difference is −180 degrees or less, the provisional electrical angle is stored in the register A516, and the data in the register B518 is further added by 1 and stored.

  The integral type phase difference measurement circuit 51 outputs the values of the register A516 and the register B518 to the electrical angle-position conversion circuit 52 as electrical angle data. The electrical angle-position conversion circuit 52 performs conversion from an electrical angle to a position (rotation angle).

  According to the fact that one of the excitation electrode groups corresponds to an electrical angle of 360 degrees, if the number of excitation electrode groups is N, the current position of the object to be measured is (register B) * 360 / N + (register A ) / N [degree].

FIG. 12 shows an algorithm for processing for obtaining electrical angle data.
[Step S1] The difference d between the provisional electrical angle data output from the voltage-electrical angle conversion circuit 515 and the previous provisional electrical angle data stored in the register A is calculated.
[Step S2] It is determined whether the difference d calculated in Step S1 is greater than -180 degrees and less than +180 degrees. If the result is positive, the process proceeds to Step S3. If the result is false, the process proceeds to step S5.
[Step S3] The provisional electrical angle data is stored in the register A.
[Step S4] The register A value stored in the register A and the register B value stored in the register B are output as the electrical angle data to the electrical angle-position converting circuit 52 that calculates the position data.

[Step S5] It is determined whether the difference d calculated in Step S1 is -180 degrees or less. If the result is positive, the process proceeds to Step S6. If the result is false, the process proceeds to step S9.
[Step S6] Add 1 to the register B value stored in the register B and store it.
[Step S7] The provisional electrical angle data is stored in the register A.
[Step S8] The register A value stored in the register A and the register B value stored in the register B are output as the electrical angle data to the electrical angle-position converting circuit 52 that calculates the position data.
[Step S9] 1 is subtracted from the register B value stored in the register B and stored.
[Step S10] The provisional electrical angle data is stored in the register A.
[Step S11] The register A value stored in the register A and the register B value stored in the register B are output as the electrical angle data to the electrical angle-position converting means 52 for calculating the position data.

It is a figure explaining a stator. It is a figure explaining a mover. It is a schematic block diagram of an electrostatic capacitance type position detector. It is a figure explaining the relationship between the phase of the reference signal input into a phase detection circuit, and the detection signal detected by the receiving electrode of a stator. 1 is a schematic block diagram of the present invention. It is a schematic block diagram of an integral type phase difference measuring circuit. It is a figure explaining the signal waveform in each part. It is a figure explaining a feature point. It is a figure which shows the example (the 1) of a current supply circuit. It is a figure which shows the example (the 2) of a current supply circuit. It is a figure explaining the example of a time gate circuit. This is an algorithm of processing for obtaining electrical angle data.

Explanation of symbols

S1 Reference signal S2 Detection signal S3 Time gate signal S4 Temporary electrical angle data S5 Electrical angle data vc Capacitor voltage i Constant current v Sample voltage A A phase B B phase C C phase D D phase 10 Stator
DESCRIPTION OF SYMBOLS 11 Excitation electrode 12 Conducting conductor 13 Feeding conductor 14 Reception electrode 15 Stator through-hole 16 Excitation electrode group 17 Detection signal output part 18a A phase feeding part 18b B phase feeding part 18c C phase feeding part 18d D phase feeding part 20 Movable element
DESCRIPTION OF SYMBOLS 21 Coupling electrode 22 Transmitting electrode 23 Through-hole of moving element 30 Excitation circuit 32,33 Waveform shaper 40 Phase detection circuit 51 Integral type phase difference measurement circuit 510 Time gate circuit 511 Current supply circuit 512 Capacitor 513 Hold / sample circuit 514 Discharge circuit 515 Voltage-electrical angle conversion circuit 516 Register A
517 Difference comparison processing unit 518 Register B
52 Electric Angle-Position Conversion Circuit 100 Capacitance Type Position Detector

Claims (3)

A stator and a movable element that moves relative to the stator;
The stator has a plurality of sets of excitation electrodes that are arranged periodically and are electrically independent of each other, and a receiving electrode that is electrically independent of the excitation electrodes.
The movable element includes a plurality of coupling electrodes periodically arranged to face the excitation electrode group, and a transmission arranged to face the receiving electrode to which all of the plurality of coupling electrodes are electrically connected. An electrode,
The moving element has the same number of coupling electrodes as the excitation electrode group,
A detection signal detected by the receiving electrode that changes depending on the relative position of the stator and the moving element, and an excitation signal having the same frequency and a different phase is applied to each excitation electrode of the excitation electrode group, and the excitation A phase difference measuring circuit for measuring a phase difference with a reference signal which is any one of excitation signals applied to the electrodes;
A capacitive position detector that detects a relative position of the moving element based on the phase difference measured by the phase difference measuring circuit;
The phase difference measuring circuit is
In the first case where the predetermined state of the reference signal and the detection signal is established, output of a predetermined current is started, and in the second case where the state of the predetermined reference signal and the detection signal is established A current supply circuit for stopping current output;
A capacitor for storing current from the current supply circuit;
A hold / sample circuit for holding and sampling the voltage across the capacitor in the second case and outputting a completion signal after completion of sampling;
A discharge circuit for discharging the charge accumulated in the capacitor in response to a completion signal of the hold / sample circuit;
A voltage-electrical angle conversion circuit that converts the voltage data obtained by the sampling into electrical angle data corresponding to a phase difference, and outputs temporary electrical angle data;
Two registers, register A and register B, for storing electrical angle data;
A difference comparison processing unit that evaluates the relationship between the provisional electrical angle data and the previous provisional electrical angle data stored in the register A;
The difference comparison processing unit
With respect to the time interval for numerically acquiring the phase difference, the absolute value of the speed of the moving element is used under a condition that is less than a value obtained by dividing 1/2 period of one excitation electrode group by the time interval.
If the electrical angle change, which is the difference obtained by subtracting the previous provisional electrical angle data from the provisional electrical angle data, is greater than −180 degrees and less than +180 degrees, the data held in the register B is not updated, Update the data held in the register A to the provisional electrical angle data,
If the electrical angle change amount is -180 degrees or less, add one cycle to the data held in the register B, update the data held in the register A to the provisional electrical angle data,
When the electrical angle change amount is +180 degrees or more, one cycle is subtracted from the data held in the register B, the data held in the register A is updated to the provisional electrical angle data,
The data of the register A is output as electrical angle data within one cycle, and the data of the register B is output as cycle number data.
A conversion circuit for converting the output from the phase difference measurement circuit into position data;
An electrostatic capacitance type position detector. A time gate circuit that outputs a binary time gate signal having the meanings of “valid” and “invalid”;
The time gate signal is a signal that becomes valid with a feature point that appears once in one cycle of a predetermined reference signal, and becomes invalid with a feature point that appears once in one cycle of the predetermined detection signal. ,
The current supply circuit is controlled to output a predetermined current when the time gate signal is valid,
The hold / sample circuit is controlled to perform a hold operation and a sampling operation when the time gate signal becomes invalid after the time gate signal becomes valid. Capacitive type position detector. A time gate circuit that outputs a binary time gate signal having the meanings of “valid” and “invalid”;
The time gate signal is a signal that becomes valid with a feature point that appears once in one cycle of the predetermined detection signal, and is invalid with a feature point that appears once in one cycle of a predetermined reference signal. ,
The current supply circuit is controlled to output a predetermined current when the time gate signal is valid,
The hold / sample circuit is controlled to perform a hold operation and a sampling operation when the time gate signal becomes invalid after the time gate signal becomes valid. Capacitive type position detector.

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